Synthesis of polypyrrolinones on solid support

[reaction: see text] An efficient, three-step iterative synthesis of polypyrrolinones has been achieved on solid support, setting the stage for the construction of a wide variety of libraries based on the pyrrolinone scaffold. Central to the approach is an effective end-game sequence featuring pyrrolinone ring construction with traceless release from the solid support.

A second-generation synthesis of polypyrrolinone nonpeptidomimetics: prelude to the synthesis of polypyrrolinones on solid support

[reaction: see text] A second-generation asymmetric synthesis of polypyrrolinones (3) has been achieved exploiting scalemic alpha-aminolactones (1) as building blocks. Imine formation between an appropriate lactone (1) and aldehyde (2), followed in turn by pyrrolinone ring construction promoted by KHMDS in the presence of 18-crown-6 and modified Swern oxidation furnished pyrrolinone aldehyde 3. This iterative, efficient three-step protocol paves the way for the synthesis of polypyrrolinones on solid support.

Total synthesis of the ansamycin antibiotic (+)-thiazinotrienomycin E

The first total synthesis of (+)-thiazinotrienomycin E (1), member of a novel class of cytotoxic ansamycin antibiotics, has been achieved. Key features of the synthetic strategy include (a) the efficient construction of sulfone 7 incorporating TBS protection of the aniline, (b) an improved synthesis of allyl chloride (-)-6, the advanced intermediate employed in our trienomycins A and F total syntheses, (c) application of the Kocienski modified Julia protocol to elaborate the E,E,E-triene subunit in a stereo-controlled fashion, (d) an efficient union of sulfone 7 with advanced iodide 62, and (e) Mukaiyama macrolactamization to access the thiazinotrienomycin macrocyclic ring.

Failure to establish linkage on the X chromosome in 301 families with schizophrenia or schizoaffective disorder

The hypothesis that a gene for susceptibility to psychosis (specifically in the X-Y homologous class) is located on the sex chromosomes has been proposed. Such a gene would account for the excess of sex chromosome anomalous males and females in populations of patients with psychosis, a tendency towards concordance by sex within families, and sex differences associated with psychosis and its underlying brain pathology. In earlier studies we observed small positive LOD scores in Xp11, and in a more recent and larger cohort of 178 sibling pairs, a peak multipoint nonparametric LOD score of 1. 55 at the locus DXS8032 in Xq21. The present study with a new set of markers extended the cohort to 301 ill sibling pairs and their parents. Despite the increase in sample size, the LOD score did not increase. A peak NPL of 1.55 was observed at the locus DXS1068 in proximal Xp, a region remote from the previous report. Separating families into those who were more likely to have X chromosome inheritance (maternal with no male to male transmission) did not yield stronger findings. In spite of the evidence that psychosis is related to a sex-dependent dimension of cerebral asymmetry, it is concluded that no consistent linkage of schizophrenia to the X chromosome can be demonstrated. In the context of the general failure of replication of linkage in psychosis, the possibility that the genetic predisposition to psychosis is contributed to by epigenetic modification rather than variations in the nucleotide sequence has to be considered.

Investigation of a candidate gene for schizophrenia on Xq13 previously associated with mental retardation and hypothyroidism

Weak support for linkage of schizophrenia to proximal Xq has previously been reported. In addition, an increased prevalence of thyroid disorder has been noted in families of individuals with schizophrenia. Recently, a gene mapped to Xq13 termed HOPA has been found to be associated with mental retardation, hypothyroidism, and depression and to function as a coactivator for the thyroid receptor. We therefore examined the HOPA gene in a group of 111 probands from a larger cohort of multiplex families with schizophrenia, several of whom (n = 53) also had a family history of hypothyroidism. Four males and two females were found with an alteration in exon 42 of the HOPA gene compared with 8/492 males and 18/471 females (942 X chromosomes) compared with consecutively screened newborns (chi(2) = 3.92, P < 0.05). However, when available family members of each of the probands with an exon 42 variation were subsequently screened, the mutation did not segregate with schizophrenia in three of five families, although all 6 probands with an exon 42 variation did have hypothyroidism in either themselves (n = 3) or their mothers (n = 3) (P < 0.008). These findings replicate prior findings demonstrating an association between HOPA polymorphisms and hypothyroidism. In addition, the increased frequency of HOPA variants in this population may also provide a genetic basis for the familial association of thyroid disease and schizophrenia.

Chiral action at a distance: remote substituent effects on the optical activity of calyculins A and B

[structure--see text] Calyculins A and B differ only by the (E)- vs (Z)-configuration at C(2). Yet, they show a large difference in optical rotations. We demonstrate a new strategy that provides a physical analysis of this long-range chiro-optical effect by Boltzmann-averaged atomic contribution mapping. The polarizability characteristics of the CN substituent rather than the perturbation of the stereogenic centers or the introduction of asymmetry into the polyene chain give rise to the remarkable difference in rotation angles.

Taxol and discodermolide represent a synergistic drug combination in human carcinoma cell lines

Recently, three natural products have been identified, the epothilones, eleutherobin, and discodermolide, whose mechanism of action is similar to that of Taxol in that they stabilize microtubules and block cells in the mitotic phase of the cell cycle. In this report, we have compared and contrasted the effects of these new agents in Taxol-sensitive and -resistant cell lines. We also have taken advantage of a human lung carcinoma cell line, A549-T12, that was isolated as a Taxol-resistant cell line and found to require low concentrations of Taxol (2-6 nM) for normal cell division. This study then examined the ability of these new compounds to substitute for Taxol in sustaining the growth of A549-T12 cells. Immunofluorescence and flow cytometry have both indicated that the epothilones and eleutherobin, but not discodermolide, can substitute for Taxol in this Taxol-dependent cell line. In A549-T12 cells, the presence of Taxol significantly amplified the cytotoxicity of discodermolide, and this phenomenon was not observed in combinations of Taxol with either the epothilones or eleutherobin. Median effect analysis using the combination index method revealed a schedule-independent synergistic interaction between Taxol and discodermolide in four human carcinoma cell lines, an effect that was not observed between Taxol and epothilone B. Flow cytometry revealed that concurrent exposure of A549 cells to Taxol and discodermolide at doses that do not induce mitotic arrest caused an increase in the hypodiploid population, thereby indicating that a possible mechanism for the observed synergy is the potentiation of apoptosis. Our results suggest that Taxol and discodermolide may constitute a promising chemotherapeutic combination.

Lack of evidence for linkage to chromosomes 13 and 8 for schizophrenia and schizoaffective disorder

A previous report [Blouin et al., 1998: Nat Genet 20:70-73] suggesting linkage to chromosomes 13q32 and 8p21 in families with schizophrenia led us to investigate these regions in a large set of 301 multiplex families with schizophrenia. Multipoint analyses failed to reveal evidence for linkage to any portion of chromosome 13, while only a weakly positive score was present on 8p using the identical marker reported in the earlier report. Failure to confirm the Blouin et al claims in a substantially larger cohort adds emphasis to the inconsistency of the findings concerning linkage in schizophrenia. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 96:235-239, 2000.

Calcium channels controlling acetylcholine release from preganglionic nerve terminals in rat autonomic ganglia

Little is known about the nature of the calcium channels controlling neurotransmitter release from preganglionic parasympathetic nerve fibres. In the present study, the effects of selective calcium channel antagonists and amiloride were investigated on ganglionic neurotransmission. Conventional intracellular recording and focal extracellular recording techniques were used in rat submandibular and pelvic ganglia, respectively. Excitatory postsynaptic potentials and excitatory postsynaptic currents preceded by nerve terminal impulses were recorded as a measure of acetylcholine release from parasympathetic and sympathetic preganglionic fibres following nerve stimulation. The calcium channel antagonists omega-conotoxin GVIA (N type), nifedipine and nimodipine (L type), omega-conotoxin MVIIC and omega-agatoxin IVA (P/Q type), and Ni2+ (R type) had no functional inhibitory effects on synaptic transmission in both submandibular and pelvic ganglia. The potassium-sparing diuretic, amiloride, and its analogue, dimethyl amiloride, produced a reversible and concentration-dependent inhibition of excitatory postsynaptic potential amplitude in the rat submandibular ganglion. The amplitude and frequency of spontaneous excitatory postsynaptic potentials and the sensitivity of the postsynaptic membrane to acetylcholine were unaffected by amiloride. In the rat pelvic ganglion, amiloride produced a concentration-dependent inhibition of excitatory postsynaptic currents without causing any detectable effects on the amplitude or configuration of the nerve terminal impulse. These results indicate that neurotransmitter release from preganglionic parasympathetic and sympathetic nerve terminals is resistant to inhibition by specific calcium channel antagonists of N-, L-, P/Q- and R-type calcium channels. Amiloride acts presynaptically to inhibit evoked transmitter release, but does not prevent action potential propagation in the nerve terminals, suggesting that amiloride may block the pharmacologically distinct calcium channel type(s) on rat preganglionic nerve terminals.

Cyclic peptide formation catalyzed by an antibody ligase

Cyclic hexapeptides represent a class of compounds with important, diverse biological activities. We report herein that the antibody 16G3 catalyzes the cyclization of d-Trp-Gly-Pal-Pro-Gly-Phe small middle dotp-nitrophenyl ester (8a) to give c-(d-Trp-Gly-Pal-Pro-Gly-l-Phe) (11a). The antibody does not, however, catalyze either epimerization or hydrolysis. The resulting rate enhancement of the cyclization by 16G3 (22-fold) was sufficient to form the desired product in greater than 90% yield. In absolute rate terms, the turnover of 16G3 is estimated to be 2 min(-1). The background rate of epimerization of 8a was reduced from 10 to 1% and hydrolysis from 50 to 4% in the presence of 16G3. As expected, the catalytic effects of 16G3 were blocked by the addition of an amount of the hapten equal to twice the antibody concentration. We also synthesized three diastereomers of 8a: the d-Trp(1)-d-Phe(6) (8b), l-Trp(1)-l-Phe(6) (8c), and l-Trp(1)-d-Phe(6) (8d) hexapeptides as well as d-Trp'-l-Trp(6) (12) and d-Phe'-l-Phe(6) (13). As expected, the rate enhancement by 16G3 was greatest for 8a, because the stereochemistry of Trp(1) and Phe(6) matches that of the corresponding residues on the hapten used to induce the biosynthesis of 16G3. A model of the variable domain of 16G3 was generated from the primary sequence using the antibody structural database to guide the model construction. The resulting model provided support for some previously proposed interpretations of the kinetic data, while providing valuable new insights for others.

Novel ligands lacking a positive charge for the delta- and mu-opioid receptors

Recently we reported using minilibraries to replace Lys(9) [somatostatin (SRIF) numbering] of the potent somatostatin agonist L-363,301 (c[-Pro-Phe-D-Trp-Lys-Thr-Phe-]) to generate the potent neurokinin receptor (NK-1) antagonist c[-Pro-Phe-D-Trp-p-F-Phe-Thr-Phe-]. This novel cyclic hexapeptide did not bind the SRIF receptor. Thus, a single mutation converted L-363,301, a SRIF agonist with potency ca. 2-8 times the potency of SRIF in laboratory animals,(24) into a selective NK-1 receptor antagonist with an IC(50) of 2 nM in vitro. During the screening of the same libraries for ligands of the delta-opioid receptor, we identified four compounds (1-4) which represent a new class of delta-opioid antagonists, some of which were also NK-1 receptor antagonists. The most potent delta-opioid antagonist, c[-Pro-1-Nal-D-Trp-Tyr-Thr-Phe-] (2), showed a K(e) value of 128 nM in the mouse vas deferens assay and a delta-receptor binding affinity constant of 152 nM in the rat brain membrane binding assay. These results are of interest because they represent a novel class of delta-opioid antagonists and, like two previously reported delta-opioid antagonists, they lack a positive charge. To examine further the requirement for a positive charge in the delta-opioid ligands, we prepared two analogues of the beta-casomorphin-derived mixed mu-agonist/delta-antagonist, H-Dmt-c[-D-Orn-2-Nal-D-Pro-Gly-] (7), in which we eliminated the positive charge either through formylation of the primary amino group (5) or by the deletion of this N-terminal amino group (6). These latter compounds proved to be delta-opioid antagonists with K(e) values in the 16-120 nM range, as well as fairly potent mu-opioid antagonists (K(e) approximately 200 nM). These six compounds provide the most convincing evidence to date that there is no requirement for a positive charge in mu- and delta-opioid receptor antagonists. In addition, cyclic hexapeptide 4 lacks a phenolic hydroxyl group. Taken together, these data suggest that the prevailing assumptions about delta- and mu-opioid receptor binding need revision and that the receptors for these opioid ligands have much in common with the NK-1 and somatostatin receptors.

Developing a controlled vocabulary for use in a hospital information system

In bringing a controlled vocabulary to a health information system, it is important to include those terms commonly used by those who must routinely input data to the system. We have developed a methodology whereby we can obtain "free text" descriptions of diagnoses entered by system users. We then sort those terms/concepts by system and find the appropriate "atomic" term(s). The terms are also being submitted to domain experts for appropriateness and fidelity. These concepts are then coded in an international coding system (SNOMED International) to eventually be entered into the controlled "pick list" of terms available for users to enter.

Multicomponent linchpin couplings of silyl dithianes: synthesis of the Schreiber C(16-28) trisacetonide subtarget for mycoticins A and B

[formula: see text] An efficient synthesis of trisacetonide (+)-11, the Schreiber C(16-28) subtarget for mycoticins A and B, is described. The key synthetic transformation entails a one-flask, five-component linchpin coupling tactic.

Gram-scale synthesis of (+)-discodermolide

[formula: see text] A triply convergent, highly efficient second-generation synthesis of the potent antimitotic agent (+)-discodermolide (1) has been achieved on a 1-g scale.

Calcium channels controlling acetylcholine release in the guinea-pig isolated anterior pelvic ganglion: an electropharmacological study

An electropharmacological analysis of the type(s) of calcium channel controlling neurotransmitter release in preganglionic sympathetic nerve terminals in the guinea-pig anterior pelvic ganglion has been carried out. Conventional intracellular recording techniques were used to record excitatory postsynaptic potentials as a measure of neurotransmitter release. Excitatory postsynaptic potentials were abolished by hexamethonium (30-100 microM) and are therefore mediated by acetylcholine acting at nicotinic receptors. In studies of more than 150 cells, the N-type calcium channel blocker omega-conotoxin GVIA (100-300 nM) failed to block the initiation of the nerve impulse by the excitatory postsynaptic potential. In single-cell studies, omega-conotoxin GVIA (1 microM) sometimes altered the configuration of the excitatory postsynaptic potential/cell body nerve action potential complex, but on only one occasion was the excitatory postsynaptic potential reduced below the threshold required to initiate the action potential. Nifedipine (10 microM), omega-agatoxin IVA (100 nM) and omega-conotoxin MVIIC (300 nM), applied alone or in combination with omega-conotoxin GVIA (300 nM), were also ineffective. However, excitatory postsynaptic potentials evoked by trains of stimuli (0.1-0.5 Hz) were markedly reduced or abolished by the non-specific calcium channel blocker omega-grammotoxin SIA (300 nM). When trains of stimuli were delivered at higher frequencies (4 Hz), the block induced by omega-grammotoxin SIA could be overcome, and excitatory postsynaptic potentials were able to initiate action potentials even when omega-conotoxin GVIA, omega-agatoxin IVA and omega-conotoxin MVIIC were also present. The calcium channel(s) controlling acetylcholine release was (were) blocked by low concentrations of cadmium ions (30 microM) at all stimulation frequencies studied (0.1-50 Hz). Thus, the dominant calcium channels controlling acetylcholine release in sympathetic ganglia are not the L, N, P or Q types. At low frequencies of stimulation, omega-grammotoxin SIA-sensitive calcium channels play a dominant role in acetylcholine release, but at higher stimulation frequencies yet another pharmacologically distinct calcium channel (or subtype) supports neurotransmitter release.

Total synthesis of (+)-thiazinotrienomycin E

[formula: see text] The first total synthesis of (+)-thiazinotrienomycin E (1), member of a novel class of cytotoxic ansamycin antibiotics, has been achieved. The synthesis features a highly efficient construction of the aromatic fragment 3 incorporating TBS protection of the aniline, a significantly improved synthesis of (-)-19, an intermediate employed in our trienomycins A and F total syntheses, application of the Kocienski modified Julia protocol to elaborate the E,E,E-triene subunit, an efficient union of 3 and (+)-4, and Mukaiyama macrolactamization to access the thiazinotrienomycin macrolide.

Tremorgenic indole alkaloids. Studies directed toward the assembly of the A, F, and I rings of penitrem D: observation of an unexpected stereochemical outcome

[formula: see text] In this Letter we demonstrate the viability of a highly stereoselective tandem Mannich cyclization-grammine fragmentation/addition cascade, critical for assembly of the A and F rings of penitrem D. We also explored simultaneous execution of this tactic with concurrent construction of ring I. Reinvestigation of a model system provided an explanation for the unanticipated stereochemical outcome at C(28).

Synthesis and biological activity of cyclic peptide inhibitors of ribonucleotide reductase

[formula: see text] A series of lactam-bridged peptide inhibitors (2-6) of mammalian ribonucleotide reductase (mRR) has been designed and synthesized on the basis of the heptapeptide N-AcFTLDADF (1), corresponding to the C-terminus of the R2 subunit of mRR. Inhibition studies revealed a direct relation between ring size and activity, with peptide 5 being 2.5 times more potent than peptide 1.

Synthesis of tedanolide and 13-deoxytedanolide. Assembly of a common C(1)-C(11) subtarget

[formula: see text] In this Letter we describe a synthetic strategy and an efficient assembly of a common C(1)-C(11) subtarget, (-)-3, for (+)-tedanolide (1) and (+)-13-deoxytedanolide (2), architecturally complex marine macrolides displaying potent antitumor activity. Key elements of the synthesis include two iterations of the Evans aldol protocol to construct the C(1)-C(6) moiety and a stereocontrolled vinyl anion addition to generate the C(8,9) trisubstituted olefin incorporating stereogenicity at C(7). Alkylation with a model epoxide demonstrates that (-)-3 is a competent dithiane for further elaboration of the macrolide skeleton.

Phorboxazole synthetic studies. 2. Construction of a C(20-28) subtarget, a further extension of the Petasis-Ferrier rearrangement

[formula: see text] In this, the second of two Letters, we describe the efficient assembly of (+)-4, a C(20-28) subtarget for the total synthesis of phorboxazoles A (1) and B (2). The synthesis was achieved in 12 linear steps (20% overall yield) via Petasis-Ferrier rearrangement of an E/Z mixture of trisubstituted enol ethers (15) to assemble the C(22-26) cis-tetrahydropyran. A mechanism for the observed diastereoconvergence of 15 is proposed. In addition, a new tactic for the synthesis of enol ethers (e.g., 15) based on the elegant work of Julia is described.

Phorboxazole synthetic studies. 1. Construction of a C(3-19) subtarget exploiting an extension of the Petasis-Ferrier rearrangement

[formula: see text] In this, the first of two letters, we outline our overall strategy for the total synthesis of phorboxazoles A (1) and B (2), rare oxazole-containing macrolides possessing extraordinary antimitotic activity, and describe the assembly of a C(3-19) subtarget (-)-5 for the total synthesis of phorboxazole A. The synthesis of (-)-5 was achieved in 15 linear steps (12% overall yield), exploiting a modification of the Petasis-Ferrier rearrangement to construct the C(11-15) cis-tetrahydropyran. Dimethylaluminum chloride (Me2AlCl) proved to be the Lewis acid of choice for the Petasis-Ferrier rearrangement.

Pressure-overload-induced sliding hiatal hernia in power athletes

Sliding hiatal hernias are a common condition thought to occur with increasing age secondary to a degenerative process. The incidence of sliding hiatal hernias in the general population is 0.5%. Although the prevalence in the Western world is thought to be significantly higher, with approximately 60% of geriatric patients in North America having a hiatal hernia on radiologic studies. Thus, the primary etiology of the sliding hiatal hernia is thought to be degeneration of the phrenoesophageal ligament. Most hiatal hernias occurring in young adults are idiopathic. There has been speculation of a stress-induced hiatal hernia from repeated episodes of elevated intra-abdominal pressure, and to date there is one report of a pressure-overload-induced hiatal hernia occurring in an elite body builder. The prevalence of hiatal hernia in young male power athletes has yet to be examined. Therefore, we examined eight male elite power athletes and seven male non-weightlifters, matched for age, via fluoroscopy with barium swallow to test the hypothesis that pressure overload can induce hiatal hernias in young adults.